Types of Chlorination

Types of chlorination
The different types of chlorination are:

1. Plain chlorination
2. Pre-chlorination
3. Post-chlorination
4. Double chlorination
5. Break-point chlorination
6. Super chlorination
7. Dechlorination

• Plain chlorination is where ONLY chlorine is applied to water and no other treatment is given
• Plain chlorination is carried-out only in cases of emergency
• Dose is approximately 0.5 mg/l

• Pre-chlorination refers to application of chlorine to water PRIOR to any other treatment
• Dosage varies from 0.10 to 0.50 mg/l

• Post-chlorination refers to chlorination AFTER all the treatment has taken place.
• Dosage varies from 0.10 to 0.20 mg/l

• Double chlorination refers to application of chlorine to water at more than one point

• Break-point chlorination refers to the dosage beyond which any further addition of chlorine appears as free residual chlorine

• Super chlorination refers to application of chlorine beyond the stage of break-point chlorination
• Dosage varies from 5 to 15 mg/l

• Dechlorination refers to removal of chlorine from water
• This is required after super-chlorination
• During dechlorination, sufficient care should be taken so that sufficient residual chlorine remains in water
• Examples of dechlorinating agents are: SO2 gas, Activated Carbon, Sodium thio sulphate (Hypo) and sodium sulphate.